For the production of yeast extract, typically baker's and torula yeast cells may be subjected to autolysis. Some sources of yeast (e.g. spent brewer's yeast) contain residues of gluten (gliadins). As a consequence, extracts and suspensions derived of yeasts sources containing gliadins have limited use in food applications due to the intolerance towards gliadins in part of the population (Celiac disease). It was observed that typical yeast extracts or autolysates obtained from sources containing gliadins (e.g. brewer's yeast extracts) contain gliadins in a concentration exceeding the acceptable threshold of 20 ppm by weight.
Reduction of gliadins from yeast sources containing gliadins enables the use of these yeasts and extracts thereof is food applications which require absence of low concentrations of gluten.
A problem with the reduction of gliadins in yeast is to reduce specifically the gliadin content without undesired side effects of the treatment. For example, it is undesired that the treatment aiming to reduce the gliadin content also degrades the yeast′ RNA.
It was now surprisingly found that gliadins can be removed from a yeast source containing gliadins by incubation with a proline-specific endoprotease during the hydrolysis and/or autolysis process. It was surprisingly found that the gliadins can effectively be hydrolyzed to a level below 20 ppm by weight on dry matter content of the yeast autolysates and extracts. Further, it was found that incubation with a proline-specific endoprotease during the hydrolysis and/or autolysis process did not degrade the RNA present in the yeast.